Biostratigraphy

1. Biostratigraphy زیست چینه نگاری نوع درس : اصلی تعداد واحد :2 مقطع تحصیلی کارشناسی ارشد چینه نگاری و دیرینه شناسی Prepared by:Dr.MohammadN.Gorgij Geology Department University of Sistan and Baluchestan

2. :سرفصل • - تاریخچه وچگونگی پیدایش زیست چینه نگاری و فواید آن • - تعاریف و مفاهیم اصلی در زیست چینه نگاری • - مطالعه پیدایش و از بین رفتن ریز فسیلهای شاخص و فسیل های همراه • -تهیه نمودار انتشار گونه های ریز فسیلی شاخص • - ایجاد زونهای ریز فسیلی شاخص • - تعیین سن نسبی سازند بر مبنای انتشار چینه شناختی آنها • - انواع واحدهای اصلی در زیست چینه نگاری • - زون بندی در صنعت نفت و تفاوت آن بازون بندی در رخنمونها • - مطالعه وشناخت زون های جهانی بر اساس پیدایش و انقراض گرو ه ها • - شناخت و مطالعه چرایی انقراض بعضی گروه ها در زمان های مشخص • - همبستگی نموداری (Graphic Correlation(

3. فهرست منابع : 1- McGowran,2005. Biostratigraphy,Microfossils and Geological Time,Cambridge University Press. 2 –Zigler, 1988. Introduction to Paleobiology : General Paleontology, University College of London. 3 - Rich, T. H. 1994. Wild life of Gondwana, The 500 Million Years history of vertebrate animals from the ancient southern Supercontinent,Reedbook. 4 - Truck,J. Mark,J. Benes, 1988. Fossils of the world : Comprehensive practical guide to collecting and studying Fossils, Arch Cape Press, New York.

6. Speciation • Speciation refers to the process by which new species are formed. • Speciation occurs when gene flow has ceased between populations where it previously existed. • Speciation is brought about by the development of reproductive isolating mechanisms which maintain the integrity of the new gene pool. • The separate populations may be exposed to different selecting pressures, • Genetic drift may produce different changes in each population • Mutation may result in new alleles

7. Splitting & Budding • Taking a very simple view, speciation can happen in one of two ways: • Splitting: A species could split fairly equally into two populations that evolve differently until they eventually become separate species. • Budding: A small part of the species population could “bud off” from the main part and evolve rapidly (in geological time-scale terms) to form a new species while leaving most of the original species population unchanged. B A B C Species B Species C Species A Species B Population splits equally Small population buds off A A Species A Species A Splitting Budding

8. Types of Speciation • Several models have been proposed to account for new species among sexually reproducing organisms: • Allopatric speciation: Populations become geographically separated, each being subjected to different natural selection pressures, and finally establishing reproductive isolating mechanisms. • Sympatric speciation: A population forms a new species within the same area as the parent species. • Parapatric speciation: The speciating populations are only partially separated geographically, so some individuals on each side are able to meet across a common boundary during the speciation process. • Peripatric speciation: A small founding population enters an isolated niche.

9. Allopatric Speciation 1 • STAGE 1: • Moving into new environments • Parent population expands range and occupies new parts of the environment. • Expansion of the range maybe due to competition. • Population has common gene pool with regular gene flow (any individual has potential access to all members of the opposite sex for the purpose of mating). Parent population

10. Allopatric Speciation 2 • STAGE 2: • Geographical isolation • Gradual formation of physical barriers may isolate parts of the population at the extremes of the species range • As a consequence, gene flow between these isolated populations is preventedor becomes rare. • Agents causing geographicalisolation include: • continental drift • Climatic change • Changes in sea level (due to ice ages). River barrier prevents gene flow Isolated Population B Isolated Population A Mountain barrier prevents gene flow Some natural variation exists in each population Isolated Population C

11. Allopatric Speciation 3 • STAGE 3: • Formation of a subspecies • The isolated populations may be subjected to quite different selection pressures. • These selection pressures will favor those individuals with traits suited to each environment. • Allele frequencies for certain genes change andthe populations take on the status of a subspecies (reproductive isolation is not yet established). Wetter climate Cooler climate Sub-species A Sub-species A Drier climate Sub-species C

12. Allopatric Speciation 4 • STAGE 4: • Reproductive isolation • Each separated subspecies undergoes changes in its genetic makeup and behavior. This will prevent mating with individuals from other populations. • Each subspecies’ gene pool becomes reproductively isolated from the othersand they attain species status. • Even if geographical barriers are removed to allow mixing of the populations, geneticisolation is complete. Sympatric species Species A Species B River barrier removed Mountain barrier remains Allopatric species Species A Sympatric species: Closely related species with overlapping distribution Allopatric species: Closely related species still geographically separated

13. Sympatric Speciation • Sympatric Speciation: A new species within the same area as the parent species. • There is no geographical separation between the speciating populations. • All individuals are, in theory, able to meet each other during the speciation process. • Sympatric speciation is rarer than allopatric speciation among animals, but it is probably a major cause of speciation among plants. • Sympatric speciation may ocur through: • A change in host preference, food preference or habitat preference. • The partitioning of an essential but limiting resource. • Instant speciation as a result of polyploidy (particularly among plants, as in the evolution of wheat).

14. Sympatric Speciation 1 An insect forced to lays its eggs on an unfamiliar plant species may give rise to a new population of flies isolated from the original population • A change in habitat preference: • It is not uncommon for some insect species to be conditioned to lay eggs on the plant species on which they themselves were reared. • If the normally preferred plant species is unavailable, then the insect may be forced to choose another species to lay eggs on. • A few eggs surviving on this new plant will give rise to a new population with a new plant species preference. Original host plant species New host plant species

15. Sympatric Speciation 2 Each host plant will attract flies that were reared on that plant where they will mate with other flies with a similar preference • Establishing reproductive isolation: • If mating and rearing of offspring takes place entirely within the habitat, then the population will become reproductively isolated. • Further differentiation of the two populations is likely as eachbecomes increasingly adapted to their respective habitats. • Ultimately, the two groups will diverge to be recognized as separate species. No gene flow Gene flow Original host plant species New host plant species

16. Sympatric Speciation 3 • Polyploidy involves the multiplication of whole sets of chromosomes (each set being the haploid number N). • Polyploids occur frequently in plants and in some animal groups such as rotifers and earthworms. • When such individuals spontaneously arise, they are instantly reproductively isolated from their parent population. • As many as 80% of flowering plantspecies may have originated as polyploids.

17. Marine ecosystem – modes of life • Planktonic - small plants and animals that float, drift, or swim weakly (plankton) • Phytoplankton - plants and plant-like plankton, such as diatoms and coccolithophores • Zooplankton - animals and animal-like plankton, such as foraminifera and radiolaria • Nektonic - swimming animals that live within the water column (nekton) • Benthonic or benthic - bottom dwellers, whch may be either: • Infaunal - living beneath the sediment surface; they burrow and churn and mix the sediment, a process called bioturbation • Epifaunal - living on top of the sediment surface

18. Marine Ecosystem • Where and how animals and plants live in the marine ecosystem Plankton: Jelly fish Sessile epiflora: seaweed Nekton: fish cephalopod Sessile epifauna: bivalve coral Mobile epifauna: Starfish & Gastropod Infauna- worm, bivalve

19. Stages in Species Formation Homogeneous Ancestral Population • Different types of isolating mechanisms operate and different amounts of gene flow take place as two populations diverge to form new species. Population splits Population A Population B Gene flow common Geographic isolation Geographic isolation Evolutionary Development Race A Race B Prezygotic isolation Gene flow uncommon Prezygotic isolation Subspecies B Subspecies A Gene flow very rare Postzygotic isolation Postzygotic isolation No gene flow Species A Species B

21. Punctuated Equilibrium New Species Parent Species New Species • There is abundant evidence in the fossil record that, instead of gradual change, species stay much the same for long periods (stasis) and then have short bursts of evolution that produce new species quite rapidly. • According to this punctuated equilibrium theory, most of a species existence is spent in stasis and little time is spent in active evolutionary change. New species 'bud off' from the parent species and undergo rapid change, followed by a long period of stability

22. Types of Evolution • Aims: • Must be able to define the two main forms of evolution, with examples. • Should be able to define the term speciation and outline the different forms with examples. • Could be able to outline the stages of different forms of speciation.

23. Apomorphy and plesiomorphy illustrated together What about primitive and derived characters?You might hear people use the term "primitive" instead of plesiomorphic and "derived" instead of apomorphic. However, many biologists avoid using these words because they have inaccurate connotations. We often think of primitive things as being simpler and inferior — but in many cases the original (or plesiomorphic) state of a character is more complex than the changed (or apomorphic state). For example, as they have evolved, many animals have lost complex traits (like vision and limbs). In the case of snakes, the plesiomorphic characteristic is "has legs" and the apomorphic characteristic is "doesn't have legs." Changed state Original state

24. Paraphyletic group Includes ancestor and some, but not all of its descendants Polyphyletic group Includes two convergent descendants but not their common ancestor Monophyletic group Includes an ancestor all of its descendants A B C D A B C D A B C D Taxon A and C share similar traits through convergent evolution How could this happen? Taxon A is highly derived and looks very different from B, C, and ancestor Phylogeny and classification Only monophyletic groups (clades) are recognized in cladistic classification

26. Phylogeny • The goal of systematics is to determine the phylogeny – the evolutionary history – of a species or group of related species.

27. Phylogeny • Phylogenies are inferred by identifying organismal features, characters, that vary among species. • These characters can be: • Morphological • Chromosomal • Molecular • Behavioral or ecological

28. Homology • Homologous characters are shared characters that result from common ancestry.

29. Convergent Evolution • Convergent evolution occurs when natural selection, working under similar environmental pressures, produces similar (analogous) adaptations in organisms from different evolutionary lineages.

30. Shared Primitive and Shared Derived Characteristics • Focusing on homologous structures, we need to determine when that character arose. • Newer characters tell us more! • Primitive (older) vs. derived (newer) characters

31. Shared Primitive and Shared Derived Characteristics • A shared primitive character is a homologous structure that is older than the branching of a particular clade from other members of that clade. • It is shared by more than just the taxon we are trying to define. • Example – mammals all have a backbone, but so do other vertebrates.

32. Shared Primitive and Shared Derived Characteristics • A shared derived character is a new evolutionary feature, unique to a particular group. • Example - all mammals have hair, and no other animals have hair. • These are the features that are most useful for determining evolutionary relationships!

33. Ancestral Character States • The ancestral character state is the form of the character that was present in the common ancestor of the group. • Variations of the character that arose later are called derived character states.

34. Clades • Clades are groups that share derived characters and form a subset within a larger group. • A clade is a unit of common evolutionary descent.

35. Synapomorphy • A synapomorphy is a derived character that is shared by all the members of the clade. • Using synapomorphies to define clades will result in a nested hierarchy of clades.

36. Cladogram The nested hierarchy of clades can be shown as a cladogram that is based on synapomorphies.

37. Monophyletic A valid clade is monophyletic, it consists of the ancestor species and all its descendants.

38. Paraphyletic A paraphyletic clade consists of an ancestral species and some, but not all, of the descendants.

39. Convergent Evolution • Not all similarity is inherited from a common ancestor: • Species from different evolutionary branches may resemble each other if they have similar ecological roles. • = Convergent evolution. • Similarity due to convergence is not a basis for including species in the same taxonomic group. • Example: The swimming carnivore niche. • This niche was exploited by a number of unrelated vertebrate groups at different times in the history of life. • The selection pressures of this niche produced fins or flippers and a streamlined body shape for rapid movement through the water. Reptile: icthyosaur (extinct) Fish: shark Mammal: dolphin Bird: penguin

40. Placental Mammals North America Marsupial Mammals Australia Wood chuck Wombat Flying squirrel Flying phalanger Mole Marsupial mole Mouse Marsupial mouse Wolf Tasmanian wolf Rabbit Long-eared bandicoot Convergent Evolution-Mammals • Marsupial and placental mammals have evolved separately to occupy equivalent niches on different continents; they are ecological equivalents.

41. Divergent Evolution Changes in the genetic make-up of the two species • The diversification of an ancestral group into two or more species in different habitats is called divergent evolution. • When divergent evolution involves the formation of a large number of species to occupy different niches this is called an adaptive radiation. • A hypothetical family tree showing divergence from common ancestors on two occasions is shown here: Speciation by splitting Genetic changes accumulate to form a new species Extinction Little genetic change: species remains relatively unchanged Speciation by budding Time

42. THE MOST CRITICAL FACTORS AFFECTING CHRONOSTRATIGRAPHIC SIGNIFICANCE IN BIOSTRATIGRAPHY ARE: • 1. EVOLUTION • 2. MIGRATION • 3. EXTINCTION • 4. ENVIRONMENT • 5. PRESERVATION